maintenance or restoration of normal sagittalalignment by using the Cotrel-Dubousset technique. 7 With this surgical method combined with Ponte osteotomy, 27 it is possible to correct hypokyphosis of the thoracic spine while preserving a normal LL in a notable percentage of patients with AIS. 2 , 8 , 17 Recent clinical and radiological investigations of surgically treated patients showed a correlation between the loss of normal TK and the development of CK, which was associated with frequent axial neck pain. 15 , 30 It has already been shown that sagittal plane

bodies from C-2 to C-7 and then summing the segmental angles for an overall cervical curvature angle.
Translation of the cervical spine in the sagittal plane is measured through the cervical SVA, for which there are different methods of measurement. Both C-2 SVA ( Figs. 2 and 3 left ) and C-7 SVA have been used to define sagittalalignment globally by measuring the distance between the C-2 and C-7 plumb lines, respectively, from the posterior superior corner of the sacrum. Cervical SVA can also be defined regionally using the distance between a plumb line dropped

levels above UIV. Statistical Analysis The collected demographic, surgical, and radiographic data were described and analyzed at baseline and immediate postoperative follow-up. Changes in radiographic alignment were also investigated, including a preoperative to postoperative analysis of sagittalalignment and the rate of radiographic PJK. Patients were stratified into 5 groups based on the preoperative to postoperative degree of change in LL: decrease in LL (kyphotic change > 5°), stable (change between −5° and 5°), 5°–15° increase (lordotic change of 5°–15°), 15

M uch has been written on the relationship between patient-reported outcomes and sagittalalignment in thoracolumbar deformities. 5–8 , 12 , 17 , 18 , 23 Although simple equations were initially used to identify thoracolumbar deformities, more recently, patient-specific formulas have been developed to more specifically quantify each deformity. 10 , 22 However, cervical spine studies have yet to define a fundamental equation, let alone patient-specific descriptors, that both elucidate a deformity and suggest a nidus for correction. The cervical sagittal

S pinal deformity in the adult is commonly a 3D pathology. However, evidence points toward the clinical impact of deformity being mostly related to the sagittal plane, with little correlation between coronal deformity and self-reported disability. The Classification of Adult Deformity 20 was primarily built on clinical impact parameters, and it highlights lumbar lordosis as well as global sagittalalignment. Work leading to the classification did not identify a significant clinical impact of coronal plane parameters. 20 Additionally, in the commonly known

, all of the demographic differences were similar between patients with and without preoperative cervical malalignment, with the exception of CK. Patients with CK were significantly younger by an average of 10 years. This result is in line with both Park et al. 20 and Smith et al. 25 The study by Park and colleagues assessed the effect of age on cervical sagittalalignment in 100 asymptomatic subjects and found that the C2–7 lordosis increased with age. Smith et al. also found that patients with CK were significantly younger than those without CK in a large

posterosuperior corner of the C-7 vertebral body. The horizontal line with an arrow represents the C2–7 SVA.
Given the significant impact of sagittalalignment on HRQOL among patients with thoracolumbar spinal deformities, and the studies of Tang et al. 54 and Smith et al. 45 demonstrating correlations between cervical sagittalalignment and multiple measures of HRQOL, the C2–7 SVA was selected as a modifier for the CSD classification. Based on regression analysis from Tang et al., a C2–7 SVA threshold of 4 cm was found to correlate with moderate disability based on the